A pressure-enthalpy diagram can be used to troubleshoot issues in a refrigeration system by analyzing the refrigerant’s behavior during different stages of the cycle. For example, if the system is experiencing high discharge pressures, the diagram can be used to identify the corresponding enthalpy values and determine if the refrigerant is experiencing excessive superheating. Similarly, if the system is experiencing low suction pressures, the diagram can be used to identify the corresponding enthalpy values and determine if the refrigerant is experiencing excessive subcooling. By analyzing the diagram, technicians can identify potential issues and take corrective action to optimize system performance.